The present invention relates to an image sensor having a photometric function for sensing the intensity of incident light added to the functions of a conventional image sensor. The invention further relates to an image sensor enabling multi-pattern photometry to be carried out therewith.
Photometry is carried out before taking a photograph to determine various photographing factors such as exposure, white balance, etc., in an electronic photographing apparatus such as an electronic still camera, electronic video camera, or the like, similarly to an ordinary film-type camera. For this purpose, in a conventional electronic camera, separately from a photographing sensor, a special photodiode is provided on a lens in the front side of the camera or inside the camera body behind the photographing lens.
Various methods of carrying out photometry are known, including a center-emphasis system in which the subject is placed in the center portion of the scene and an edge-portion-emphasis system in which the subject is placed in an edge portion of the scene. In an ordinary film camera, furthermore, there is known a so-called multi-pattern photometry system in which the scene is divided into a plurality of pattern areas which are suitably selectively used as objective areas for photometry according to the composition of the picture.
However, it has not heretofore been possible to provide a photometry sensor on the same chip as the photographing sensor without lowering the aperture ratio of the photographing sensor. Furthermore, in order to employ the multi-pattern photometry system in an electronic photographing apparatus such as an electronic still camera, it is necessary to either add a special device to the photometry image sensor such as a photodiode as mentioned above, provide a plurality of photometry image sensors, or distribute the incoming light through a complicated optical system. All of these techniques are, however, unsuitable if the camera is to be miniaturized because of the provision of the separate photometry sensor.